1. Field of the Invention
The present invention relates to a method and apparatus for initializing electronic units coupled to a bus in an in-flight entertainment system. More particular, the invention relates to assigning and writing addresses to a series of electrical devices connected by an interconnect bus. The assigning of addresses may be done either at initiation of the system or upon reconfiguration during maintenance of the system.
2. Description of Related Art
Over the last few decades, commercial aircraft have become a necessary mode of travel for personal and business reasons. In order to improve passenger comfort, many commercial airlines now offer on-board telephony as well as in-flight entertainment such as video games, pay-per-view movies, hotel reservations services, and the like. Such amenities require supporting electronics distributed through the aircraft. Maintenance of the sophisticated electronics in in-flight entertainment systems (IFES) is a major concern of the airlines.
Airlines value quick servicing and maintenance of aircraft. Aircraft service time is time spent on the ground which results in lost flying time and lost profits. Thus systems which allow quick repairs and facilitate turn around time are an important part of airline profitability. Designs which allow standard parts to be quickly removed and replaced without adjustments are particularly desirable because they reduce maintenance error while simultaneously shortening aircraft servicing time.
One example of a system which is designed to be easily and quickly maintained is the in-flight entertainment system (IFES) designed by Sony Trans Com Inc. of Irvine, Calif.
In the Sony design, diagnostic routines in a system management unit ("SMU") speed up the diagnostic process by identifying particular seat electronic units (SEUs) as defective. The SEUs are coupled together in a daisy chain configuration such that an output of a preceding SEU provides the input to an adjacent SEU. Although a daisy chain configuration is described, other topologies which serially pass information may be used.
Replacing malfunctioning SEUs distributed throughout the passenger section of an aircraft is a time consuming, tedious task because each replacement SEU must be reconfigured by manually assigning parameters such as an address which is unique to each SEU in the chain. Thus, it is desirable to make SEUs throughout the aircraft conform to the same design parameters so that they are easily interchangeable. Making all SEU's interchangeable without significant set-up will allow maintenance personnel to quickly swap and replace defective SEUs with standardized "off the shelf" SEUs significantly simplifying maintenance of the SEUs.
One unique parameter which prevents the rapid swapping of "off-the-shelf" SEUs is that each SEU must be assigned a unique address. Traditionally addresses for such peripheral devices were either hardwired, which impaired flexibility or were set manually by the operator using switches such as dual in line package ("DIP") switches or rotary switches. Hardwiring addresses prevents an operator from replacing a defective SEU with an "off the shelf" SEU without some adjustments. The address hardwired into a new SEU must be the same as the address in the malfunctioning SEU being replaced.
An alternative to hardwiring addresses into the SEU relies on DIP switches manually set by an operator who swaps the SEUs. However manually setting switches to a particular sequence of zeros and ones is a tedious, error prone and time consuming task that significantly slows down the maintenance process. Furthermore, the time pressure of quick aircraft turn around time increases the likelihood of operator error. Improper setting of just one dip switch binary digit will result in the associated SEU being inoperable during the flight and disabling services such as telephone communication to a number of passenger seats.
In view of the ease with which time pressured airline personnel may incorrectly set a switch and the problems associated with using hardwired switches, a quick and efficient automated method of correctly assigning addresses to a series of interconnected electronic units is needed. In particular, a system is needed which, upon initialization, can be used in the field to quickly assign a unique address to each SEU in a chain of SEUs.